Rotary operated latches which have a latching arm attached to a rotatable shaft or cam shank are widely used to latch closures such as doors and cabinet or box covers. The cam shank of the latch intersects a pan, with a handle such as a "T" handle attached to one end of the cam shank on the exterior of the pan, and a latch attached to the opposite end on the interior of the pan. Brackets are commonly welded to the interior side of the pan to support both the cam shank and a locking slide which the cam shank also intersects. The locking arm of a lock cylinder actuates the slide relative to the cam shank to control rotation of the cam shank and the latch, by holding a flattened segment of the cam shank in a narrow channel in the slide. With this type of lock mechanism, the latch cannot be moved until the locking slide is retracted by the locking arm. Thus the latch cannot be closed when in the locked condition.
Another disadvantage associated with all types of exterior mounted locking latches is the corrosive effects of exposure to weather elements. The lock cylinder is particularly vulnerable through the exposed key hole.